Speed control apparatus for the switched reluctance motor

Abstract

Disclosed here is a speed control apparatus for a switched reluctance motor (SRM) including: a current control unit generating command currents for each period; a driving unit generating a pulse width modulation (PWM) signal to allow a voltage to be applied to the SRM; a magnetic flux error calculating unit calculating a magnetic flux error; a rotor position estimating unit calculating an estimation position using the magnetic flux error to output the estimation position to the magnetic flux error calculating unit; and a mode change-over unit allowing a command position corresponding to a command speed to be input to the magnetic flux error calculating unit.

What is claimed is: 
     
       1. A speed control apparatus for a switched reluctance motor (SRM) comprising:
 a current control unit generating a command current corresponding to a deviation between a command speed and an estimation speed of a rotor in a sensorless control period and generating a command current corresponding to a magnetic flux error in an open-loop control period; 
 a driving unit calculating a period in which a voltage is applied to each phase of the SRM using the command current output from the current control unit and a rotor estimation position and generating a pulse width modulation (PWM) signal to allow the voltage to be applied to the SRM; 
 a magnetic flux error calculating unit receiving a command position according to the command speed and a detected voltage and current of the SRM to calculate the magnetic flux error in the open-loop control period and receiving the estimation position and the detected voltage and current of the SRM to calculate the magnetic flux error in the sensorless control period; 
 a rotor position estimating unit receiving the magnetic flux error from the magnetic flux error calculating unit and calculating the estimation speed of the rotor using the received magnetic flux error to output the calculated estimation speed to the current control unit and calculating the estimation position using the received magnetic flux error to output the calculated estimation position to the magnetic flux error calculating unit; and 
 a mode change-over unit allowing a command current corresponding to the magnetic flux error to be transferred from the current control unit to the driving unit and allowing the estimation position output from the rotor position estimating unit to be input to the magnetic flux error calculating unit in the open-loop control period according to a speed of the SRM and allowing a command current corresponding to the deviation between the command speed and the estimation speed of the rotor to be transferred from the current control unit to the driving unit and allowing a command position corresponding to the command speed to be input to the magnetic flux error calculating unit in the sensorless control period. 
 
     
     
       2. The speed control apparatus for a switched reluctance motor as set forth in  claim 1 , wherein the current control unit includes:
 a speed control unit generating a command current corresponding to the deviation between the command speed and the estimation speed of the rotor in the sensorless control period; and 
 a current command unit generating a command current corresponding to the magnetic flux error in the open-loop control period. 
 
     
     
       3. The speed control apparatus for a switched reluctance motor as set forth in  claim 1 , wherein the driving unit includes:
 a control unit receiving the command current and the rotor estimation position to calculate a voltage application period according to rotor positions of each phase so that the command current is applied to the SRM, thereby generating and outputting a switching signal according to the period; 
 a PWM signal generating unit receiving the switching signal output from the control unit to generate the PWM signal; and 
 a converter unit variably switching excitation states of each phase of a multi-phase stator using the PWM signal output from the PWM signal generating unit and a converter reference voltage, thereby generating a rotational torque. 
 
     
     
       4. The speed control apparatus for a switched reluctance motor as set forth in  claim 1 , wherein the magnetic flux error calculating unit includes:
 a magnetic flux estimating unit receiving the command position according to the command speed and the detected current of the SRM to calculate and output an actual magnetic flux in the open-loop control period and receives the estimation position and the detected current of the SRM to calculate and output an actual magnetic flux in the sensorless control period; and 
 a magnetic flux data unit calculating and outputting an estimation magnetic flux using the detected voltage and current of the SRM. 
 
     
     
       5. The speed control apparatus for a switched reluctance motor as set forth in  claim 1 , further comprising an inductance inflection point detecting unit detecting an inductance inflection point using the detected current of the SRM and correcting the magnetic flux error output from the magnetic flux error calculating unit using a deviation between a rotor position estimated from the detected inductance inflection point and the estimation position estimated from the rotor position estimating unit in an area in which a torque is not generated. 
     
     
       6. The speed control apparatus for a switched reluctance motor as set forth in  claim 5 , wherein the inductance inflection point detecting unit includes:
 a correction position estimating unit detecting the inductance inflection point of the SRM using the detected current of the SRM to calculate and output the rotor estimation position; 
 a magnetic flux error compensating unit outputting a position error in the rotor estimation position through the rotor position estimating unit and the rotor estimation position through the inductance inflection point by correction position estimating unit; and 
 a rotor estimation position compensating unit calculating a compensation value for an estimation magnetic flux using the position error calculated by the magnetic flux error compensating unit to compensate for the magnetic flux error calculated in the magnetic flux error calculating unit. 
 
     
     
       7. The speed control apparatus for a switched reluctance motor as set forth in  claim 1 , wherein the mode change-over unit includes:
 a change-over switch allowing the command current to be input to the driving unit and allowing the command position to be input to the magnetic flux estimating unit when an open-loop switching control signal is input and allowing the command current to be input to the driving unit and the estimation position output from the rotor position estimating unit to be input to the magnetic flux estimating unit when a sensorless switching control signal is input; and 
 an operation mode determining unit outputting the open-loop switching control signal to the change-over switch before a rotor speed of the SRM reaches a maximum speed in a hysteresis band and outputting the sensorless switching control signal to the change-over switch when the rotor speed of the SRM reaches the maximum speed in the hysteresis band.